PC won't turn on after a short run of CPU fan

Been working at computer shop for decades and knows how to fix the most common PC problems, however this is one rare case I couldn't solve with the basic troubleshooting (cleaning, clr cmos, replace with new cr2032 spare, breassembling parts, PSU swap, detached RAM and HDD). I'm still figuring whether it's the faulty mobo, CPU or both were permanently damaged because of overusage or its age (6 years to be exact) and in need of replaced with new spares.

Welcome to the Forum

Sorry, I didn't understand what is the problem.
It is on a desktop or laptop?
The CPU fan runs for a short period of time and it doesn't boot?

Desktop. Forgot to mention it 'cause I wrote it on the title (lol)
Basically, my PC runs short and immediately shuts down shortly after pressing the power button on the CPU case. The CPU fans spins for like half a second. It cannot reopen until I switch off the AVR and do it again, however no matter how many times I tried, the PC still shuts down shortly.
It must be either on CPU or MOBO.

"...is one rare case I couldn't solve with the basic troubleshooting (cleaning, clr cmos, replace with new cr2032 spare, breassembling parts, PSU swap, detached RAM and HDD)..."

Please edit your profile with the MB and CPU specs.
I'm having quite the same problem with a GA Z87 MB and a i5 4670k. In my case it runs for a minute or two then shuts down. I still didn't find out if it is the MB or the i5.
A friend had same problem and it was the i5.

georgeks said:

If you read here
System Boot Process of BIOS - Windows 7 Help Forums

and since you have already replaced the Power Supply, it appears that is CPU or mainboard.

I saw something similar years ago while at HP-could be the same issue.

It is called BGA failure (Ball Grid Array) meaning the soldering on the motherboard has developed tiny cracks.
It was far more common some years back when the switch was made from lead soldering to lead-free, as the lead-free required higher temperatures and the companies were still using the old tools.

I could be like that since my mobo kept running for 6 years since we start our business (and recently discovered that its manufacture, ECS, had long history of poor quality products). I barely remember the last time I had that issue on other PC and was fixed with replacing a new mobo.

Megahertz07 said:

Please edit your profile with the MB and CPU specs.
I'm having quite the same problem with a GA Z87 MB and a i5 4670k. In my case it runs for a minute or two then shuts down. I still didn't find out if it is the MB or the i5.
A friend had same problem and it was the i5.

I had various PCs with different brands and parts so I only put my main PC on my bio.
With your issues, it could be your PSU or AVR and need to replace them with new parts.

I'll try to buy a new mobo by next month and update this post asap.